Chronic environmental tobacco smoke (ETS) exposure, particularly from parental smoking, is associated with more severe asthma - increased incidence of emergnecy department visits, life-threatening attacks, asthma symptoms, and prolonged time to recovery from asthma exacerbations requiring hospitalization. Daily ETS exposure has been reported in as many as one-third of low socioeconomic status children with asthma in U.S. samples. We recently reported a preliminary randomized control trial of an ETS reduction intervention based on social cognitive learning theory and including ongoing objective feedback on ETS exposure in a low-income, predominantly Latino and African American sample of 87 children with asthma, which was associated with a statistically significant reduction in health care utilization for acute athma and a reduction in ETS exposure of comparable effect size as measured by parental report and the child's urine cotinine level. Replication and extension are needed to improve the intervention, validate the exposure reduction, and better understand the mechanism(s) linking the intervention to clinical outcome. We propose an 18-month randomized control trial of this intervention, tailored to parental stage of change with regard to smoking practices, in 500 ETS-exposed children with persistent asthma, 3-12 years of age, receiving care from Kaiser Permanente in Northern California. All children will be on an adequate medication regimen and receive equivalent asthma education prior to randomization. Primary outcomes will be asthma acute care utilization and urine cotinine/creatinine ratio; secondary outcomes will be caregiver readiness to change smoking behavior (stage of change), asthma functional severity, non-appearance on the Kaiser Permanente list of "high risk" asthma patients, reported prohibition of smoking within the home and other indoor/enclosed areas, reported parental smoking cessation, and reported school absences. Changes in controller medication adherence will be evaluated using a pharmacy-based dispensing index. We hypothesize that this intervention will be associated with decreased asthma crisis care utilization, lower ETS exposure, and improvements in secondary disease outcomes at follow- up when compared with usual medical care. Further, we hypothesize that decreases in urine cotinine/creatinine ratio, but not changes in controller medication adherence, will be found to be instrumental in the intervention- associated improvements in asthma crisis care utilization. Special measures will be taken to enhance the reliability of cotinine as an indicator of chronic personal exposure.